Learn / Ask The Landscape Professional
I love nasturtiums, however, when I grow them from seed in May, they grow beautifully and when they flower, they get infested with big ants that leave all their excrement on the stems and it is just gross. That not only affects the blooms but the foliage as well. I hose it off but the ants come right back. I have spoken to nursery people who have never heard of this happening. What can I do? Janice
Answer
Hi Janice, this is a good news, bad news answer to
your question. The good news is the ants are not
harming your plants, but the bad news is the ants are
there because of the aphids which are harming your
plants. I'll explain. Nasturtiums have sweet nectar
(sap) within the plant that attracts aphids. Aphids
puncture the outside of the plant and passively
feed on the sap contained in tubes called phloem
within the plant. Once punctured, the sap is forced
into the aphid's food canal and when digested, is
excreted as a sticky substance called "honeydew".
Ants love honeydew! In fact, ants love
honeydew so much that they actually guard and
herd aphids like sheep (called "farming") to collect
the most honeydew possible. In your case, the
"excrement" that you see is actually black aphids,
but aphids come in other colors too such as green,
orange, white and wooly. There are about 4,400
species of aphids known. Nasturtiums are usually
planted as a sacrificial "trap crop" near vegetable
gardens to lure sap-sucking insects like
aphids, spider mites, whiteflies and leafhoppers
away from the vegetable crop.
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About Linda Lillie
Linda K. Lillie is the President of Sprigs & Twigs, Inc, the premier
landscape design and maintenance, tree care, lawn care, stonework, and carpentry
service provider in southeastern Connecticut since 1997. She is a graduate of
Connecticut College in Botany, a Connecticut Master Gardener and a national
award winning landscape designer for her landscape design and landscape installation work.
